all: add start of netbsd/arm64 support

This works well enough to run some code natively on arm64, but not well enough for more complicated code. I've been suggested to start a pull request anyway.

Updates #30824

Change-Id: Ib4f63e0e8a9edfc862cf65b5f1b0fbf9a8a1628e
GitHub-Last-Rev: b01b105e0446e349c8d9895d3ac6918fa0cdc48c
GitHub-Pull-Request: golang/go#29398
Reviewed-on: https://go-review.googlesource.com/c/go/+/155739
Run-TryBot: Benny Siegert <bsiegert@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Benny Siegert <bsiegert@gmail.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/src/runtime/os_netbsd_arm64.go b/src/runtime/os_netbsd_arm64.go
new file mode 100644
index 0000000000..fd81eb7557
--- /dev/null
+++ b/src/runtime/os_netbsd_arm64.go
@@ -0,0 +1,24 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package runtime
+
+import "unsafe"
+
+func lwp_mcontext_init(mc *mcontextt, stk unsafe.Pointer, mp *m, gp *g, fn uintptr) {
+	// Machine dependent mcontext initialisation for LWP.
+	mc.__gregs[_REG_ELR] = uint64(funcPC(lwp_tramp))
+	mc.__gregs[_REG_X31] = uint64(uintptr(stk))
+	mc.__gregs[_REG_X0] = uint64(uintptr(unsafe.Pointer(mp)))
+	mc.__gregs[_REG_X1] = uint64(uintptr(unsafe.Pointer(mp.g0)))
+	mc.__gregs[_REG_X2] = uint64(fn)
+}
+
+//go:nosplit
+func cputicks() int64 {
+	// Currently cputicks() is used in blocking profiler and to seed runtime·fastrand().
+	// runtime·nanotime() is a poor approximation of CPU ticks that is enough for the profiler.
+	// TODO: need more entropy to better seed fastrand.
+	return nanotime()
+}